Viking?

Scanning sea off Seton harbour on Friday afternoon many large gulls were present, moving btwn fishing boats coming in from mid-Forth, and many then coming into the harbour; amongst these spotted a pale juv in flight which initially settled on the high wall but then closer on the harbourmouth wall, giving scope for careful observation. Tail very pale with hardly a hint of a band, just slightly broader brown marks towards centre, primaries pale brown, not blackish as on Herring, and overall paleness is consistent with a Herring x Glaucous hybrid, i.e. a gull from the far north. Certainly a much better candidate for a proper hybrid than last year's pale Herring, which lacked the pale fringes on primaries and had a dark tail, though current bird is a little on the small side, and without the typical Glauc dipped-in-ink bill pattern shown by many such hybrids. [Postscript - OK, some say Nelson's is strictly smithsonius x hyperboreus, the type specimen being described in Alaska (before it was realised it was a hybrid); Viking Gull has been used in Europe for argentatus x hyperboreus, but I'm not sure how definitive this is. Image galleries for Europe are hosted by Newell, Offereins, Norwegian Gulls and gull-research.org; as per comments on first, some deem birds similar to the current one just extreme argentatus, would be interested in any views (post a comment below)!] Overall totals of 200+ Herring, 13+ Great Blackback, 1 ad graellsii Lesser Blackback (perhaps Lucy again, if so now wintering here for the 6th year running) and one Kittiwake offshore; down on the Seton Sands shore a single unringed adult Med Gull amongst 200 small gulls in the pre-roost. Total 7.5 gull species?!